fix(community): Relocate .g/CONTRIBUTING.md to project dir

I think it will be easier for contributors to look at top directory
it is a common practice to have this file in expected location
and to adjust over time (eg: if repo move from github to elsewhere)

According to GH doc, it will be processed same:

https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/setting-guidelines-for-repository-contributors

Generally speaking, IMHO from sustainability perspective
IHMO it is better to prefer generic practices,
over "vendor's lock in" features.

https://en.wikipedia.org/wiki/Contributing_guidelines

Signed-off-by: Philippe Coval <[email protected]>

Author: rzr